a. Field of the Invention
The present invention is directed to buffers for use in hot tubs and spas. More particularly, the present invention is directed to a buffer for a hot tub or spa that is non-clouding and that is capable of adjusting the pH without negatively affecting either total alkalinity or the calcium content of the water. The present invention is useful because it eliminates the need for dangerous acids and/or alkalies to adjust the pH of a hot tub or spa.
b. Background
One of the desirable features of both spas and hot tubs (collectively "spas") is the heated circulating water that provides a relaxing or massage-like atmosphere. Ideally, the water in the spa must be compatible with both man and machine. Three components of the water are of particular interest. They are pH, total alkalinity and calcium content.
In a spa, it is desirable that the pH be adjusted to within the range 7.2-7.8, with a pH of 7.5 being considered ideal. A pH in a range below 7.2 leads to chemical corrosion of metallic equipment such as heaters and pumps, while a pH in a range above 7.8 can cause cloudy water and scale due to precipitation of calcium from the water. In addition, elevated pH also dramatically reduced the ability of chlorine and possibly bromine to effectively sanitize the water.
In addition, it is desirable that the spa water have a total alkalinity within the range of about 80-120 ppm. "Total alkalinity" is a measure of the alkalinity contributed by hydroxide, carbonate and bicarbonate in a natural or a treated water supply based upon titration to pH 4-5, such as with a methyl orange indicator. "Standard Methods for the Examination of Water and Waste Water," 12th Edition APHA, 1965 at p. 48-52. Total alkalinity below about 80 ppm can also cause corrosion but also increases the difficulty to maintain a proper pH. When the total alkalinity exceeds about 120 ppm an increase in cloudiness and scale formation can be realized and the pH has a tendency to constantly drift upwards.
Finally, it is desirable that the water in the spa have a calcium content of 150-300 ppm as calcium carbonate. Of the three components of interest, the calcium concentration is the most difficult to control. Calcium is easily increased, but difficult to reduce. A typical process for calcium reduction is water softening wherein sodium ions (Na+) are substituted for calcium ions (Ca++). However, calcium levels below about 100 ppm are not desirable. Low calcium (soft) water is considered aggressive and will result in the corrosion of finishes and metal fittings, such as on heaters.
Typically, the pH and total alkalinity of spa water is adjusted into the desired ranges by the addition of strong acids and/or bases (alkalies). However, strong acids and alkalies are dangerous to handle, requiring that special precautions and protective clothing be used. It is an object of the present invention to develop a composition and method that provides the desired pH and total alkalinity for spa water that does not utilize a strong acid and/or base.
One attempt at controlling the pH of spa water was provided by Robard of Atlanta, Ga. Robard's product, Perfect pH, is based upon the use of phosphate in a buffering system. While effective in adjusting pH, the Robard product dramatically increased the total alkalinity measurement and removes calcium by precipitating calcium phosphate. The result is a normal pH, a high total alkalinity measurement and negligible calcium concentration. Further, the addition of the phosphate buffer can cloud the spa water for days resulting in clogged filters or worries over clogged filters and an inability to readjust total alkalinity and calcium hardness.
Accordingly, it is an object of the present invention to provide a composition that is not only capable of controlling pH, but that does not cloud the water. It is also an object of the present invention that the composition not adversely affect the total alkalinity nor the calcium concentration of the spa water.